Wind speed and frequency vary greatly throughout the year, depending on your location. If a slight wind speed change can make a significant difference to electrical output, you must capture the strongest winds to maximize power output.

Almost all wind turbines are located on a hill or close to a lake for "strong wind." But what exactly is "strong wind"? A breeze of 9 mph (14.5 km/h) can be considered quite strong; it can make holding your umbrella difficult or it can blow your tie over your face. But think again; the power curve of a 10kW Bergey Excel-S shows almost zero power output at this speed.

Consequently, it's a bad idea to take chances when it comes to installing a turbine as mistakes can cost you a lot of money. Simply being told that a location has lots of wind is insufficient for this size of investment: a careful and detailed site study must be conducted before you actually part with your money and time.

Two standard ways to determine the wind characteristics at any site are available.  The first is to check official wind maps; the second is to conduct your own site evaluation over many months. Let's review wind assessment before discussing wind mapping and surveys.

A wind turbine only functions where there is wind. Wind causes a turbine to function, so the more wind, the better. But exactly what wind do you need? Wind requirements can change with the seasons and the type of system.

Late fall and winter can be dark and tough on PV systems, so a wind energy system can help boost power generation. But a system that requires wind as its primary or sole source needs a steady input of wind throughout the year, even in fall or winter when the home occupants are indoors more and have larger energy requirements.

Turbine manufacturers print estimated monthly or yearly energy production (kWh) for varying wind speeds and tower heights.

When the speed of the wind increases, the energy produced is increased. How does tower height affect the energy production? It is indirectly related to the wind speed. Imagine wind as water which streams over your wind turbine; if your turbine is close to the ground, there will be obstructions like rocks, trees and buildings to slow down the water creating rapids and turbulence. But when you move over the "river bed", fewer obstructions allow faster water movement to give a smoother flow. When the water flow is very smooth, it is known as laminar flow, which increases wind and water speed plus energy production. It also functions to prevent "rough air" entering the turbine, reducing stress and increasing the turbine's durability.

In general, a turbine should be placed on a tower about 30ft (9m) high with no obstruction within a 300-foot or 90 m radius. Houses and trees within a 300-foot radius should be 30 feet shorter than the tower. But trees do grow and this can affect the turbine's performance. Pruning will be required.

Tower height has great impact on power and performance. With a